Problems with pg_stat_activity view

I use PostgreSQL 9.1.9 on x86_64-unknown-linux-gnu, compiled by gcc (Debian
4.7.2-5) 4.7.2, 64-bit.

I develop some tool that tests SQL code, which involves creating (and
dropping) a lot of databases.

As of today I can reproduce following situation in 100% times:

- A database is created.
- Then I try to drop it, which fails because there is a hanging session
(up to this point there is no incorrect behaviour).

Every tutorial seems to give following advice, to issue following
statement:

SELECT pg_terminate_backend(procpid) FROM pg_stat_activity WHERE datname =
...

which I did, and still the database wouldn't drop.

After some tinkering I found that:

SELECT * FROM pg_stat_activity WHERE datname =
'drop-me7e2b9b29-12ae-43f9-94c3-1f28cdd0d781';

returns no results ('drop-me7e2b9b29-12ae-43f9-94c3-1f28cdd0d781' being
name of the database).

I guess (I have no idea really) that there is some bug in pg_stat_activity
view, because if I use function pg_stat_get_activity(NULL::integer) I will
get one connection. If I drop this connection using pg_terminate_backend I
can drop the database:

> select pg_terminate_backend(procpid) from
> pg_stat_get_activity(NULL::integer) where datid=(SELECT oid from
> pg_database where datname='drop-me7e2b9b29-12ae-43f9-94c3-1f28cdd0d781');
>
Here is psql log that shows the problem:

> postgres=# SELECT COUNT(*) FROM pg_stat_activity WHERE datname =
> 'drop-me7e2b9b29-12ae-43f9-94c3-1f28cdd0d781';
> count
> -------
> 0
> (1 row)
>
> postgres=# DROP DATABASE "drop-me7e2b9b29-12ae-43f9-94c3-1f28cdd0d781";
> ERROR: database "drop-me7e2b9b29-12ae-43f9-94c3-1f28cdd0d781" is being
> accessed by other users
> DETAIL: There are 1 other session(s) using the database.
>
postgres=# SELECT oid from pg_database where datname =
> 'drop-me7e2b9b29-12ae-43f9-94c3-1f28cdd0d781';
> oid
> --------
> 131765
> (1 row)
>
> postgres=# SELECT COUNT(*) FROM pg_stat_get_activity(NULL::integer) WHERE
> datid=131765;
> count
> -------
> 1
> (1 row)
>

I also attached html dump of three tables (in this order):
pg_stat_get_activity(NULL::integer), pg_database, pg_stat_activity.

I'm not sure where the buggy behavioiur is:

- Either pg_stat_activity does not work as intended (I guess that it
might be the case)
- Or you really should document how one should drop database with
connections (preferably in the DROP DATABASE document), as every source I
found said just do: SELECT pg_terminate_backend(procpid) FROM
pg_stat_activity WHERE datname = ..., and if this the incorrect answer it
would be good to have correct one in the documentation.